backport checks for degenerate Diffie-Hellman public exponents from

OpenSSL-0.9.8a, where they were added without a corresponding patch to
0.9.7 or an advisory!  ok theo@ markus@

1 files changed, 7 insertions, 0 deletions

diff --git a/src/lib/libcrypto/dh/dh_key.c b/src/lib/libcrypto/dh/dh_key.c
index ff125c2296..648766a6ec 100644
--- a/src/lib/libcrypto/dh/dh_key.c
+++ b/src/lib/libcrypto/dh/dh_key.c
@@ -163,6 +163,7 @@ static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
         BN_MONT_CTX *mont;
         BIGNUM *tmp;
         int ret= -1;
+        int check_result;
 
         ctx = BN_CTX_new();
         if (ctx == NULL) goto err;
@@ -182,6 +183,12 @@ static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
                 }
 
         mont=(BN_MONT_CTX *)dh->method_mont_p;
+
+        if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result)
+                {
+                DHerr(DH_F_DH_COMPUTE_KEY,DH_R_INVALID_PUBKEY);
+                goto err;
+                }
         if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key,dh->p,ctx,mont))
                 {
                 DHerr(DH_F_DH_COMPUTE_KEY,ERR_R_BN_LIB);